New Haven is a city in Adams, Jefferson, and St. Joseph townships, Allen County, Indiana, United States. It sits immediately east of the city of …New Haven is a city in Adams, Jefferson, and St. Joseph townships, Allen County, Indiana, United States. It sits immediately east of the city of Fort Wayne, the second largest city in Indiana, and is situated mostly along the southern banks of the Maumee River. The population was 15,843 as of 2022.